1. Field of the Invention
The present invention relates to a method of preparing ion exchange resin catalyst by partial neutralization of the catalyst with a promoter in a vessel or a reactor. The catalysts may be useful for producing bisphenols (e.g. bisphenol-A).
2. Description of Background and Related Art
Bisphenol-A, in general, is produced by a reaction of phenol and acetone using an ion exchange resin catalyst (e.g. a cation exchange resin catalyst) that has been partially neutralized with a promoter (e.g. an aminomercaptan promoter).
Partial neutralization (e.g. less than 100% neutralization) of the ion exchange resin catalyst, sometimes referred as “promotion”, can be accomplished by slowly adding the promoter to a well-agitated vessel or reactor containing the ion exchange resin catalyst and a fluid (e.g. water) to evenly distribute the promoter throughout the vessel or reactor. However, many bisphenol-A production plants do not have a well-agitated vessel for this purpose. Instead, various known techniques are used to add the promoter to the ion exchange resin catalyst in a fixed catalyst bed reactor immediately prior to use of the reactor for the bisphenol-A production. The promoter typically is bound to the ion exchange resin catalyst in a fixed catalyst bed reactor by an acid-base neutralization reaction or by an ion exchange process if the promoter is introduced as a salt instead of a base. Since both the acid-base neutralization reaction and the ion exchange process take place very rapidly, it is difficult to obtain an even or a uniform distribution of the promoter throughout the fixed catalyst bed using these methods.
GB 1 539 463 describes a partial neutralization of a cation exchange resin catalyst with a mercaptoamine promoter by passing a solution of the mercaptoamine (or the salt of the mercaptoamine) through a fixed catalyst bed reactor and then passing water through the fixed catalyst bed in a downflow direction for a sufficient period of time to distribute the mercaptoamine throughout the catalyst bed. GB 1 539 463 does not describe the flow rates, promoter addition rates, or acid concentrations in the water needed to provide a rapid and even distribution of the promoter.
JP 06-296871 describes a method to fill a reactor with a catalyst for manufacturing bisphenol-A which includes (i) a step to fill the reactor with an unmodified resin catalyst to form an unmodified resin catalyst filled layer in the reactor, and (ii) a step for preparing the resin catalyst by allowing a part of the unmodified resin catalyst to react with a phenol solution with sulfur-containing ammonium salt in an acidified water. JP 06-296871 does not teach recirculating the acidified fluid back to the reactor. Instead, JP 06-296871 teaches the “expelling” the water from the reactor after the water has passed through the resin catalyst layer. Therefore, JP 06-296871 discloses a one-pass method of promotion.
WO 2001-094014 describes a promotion of a catalyst in a reactor. The promotion is achieved by passing a solution of a promoter, an acid and water through the reactor. The solution contains a ketone in the water.
WO 2000-053315 and WO 2005-042154 describe injecting air or inert gas bubbles into the bottom or sides of a reactor to mix a catalyst bed while a promoter is being introduced into the reactor or after a promoter is added to the reactor.
WO 2005-021155 describes a promotion of a reactor by circulating a solution of a promoter and an acid in water through the reactor until “an equilibrium is obtained.” The equilibrium requirement is not clearly defined in WO 2005-021155.
WO 2005-102520 describes the use of a promoter, recovered from bisphenol plant wastewater, for promoting a catalyst bed.
U.S. Pat. No. 3,394,089 describes the addition of mercaptoalkylamines in an un-neutralized or salt form to a stirred aqueous slurry of ion exchange resin catalyst to obtain an evenly distributed and partially neutralized catalyst.
U.S. Pat. No. 6,723,881 describes the use of a separate agitated vessel for a promoter addition to a catalyst, followed by transferring the catalyst into a fixed bed reactor.
In summary, the prior art does not provide conditions under which rapid and even distribution of a promoter throughout an ion exchange resin catalyst bed can be obtained. The methods disclosed in the prior art would result in the use of extra equipment, longer production time, and/or higher production costs.
Therefore, there is a need in the industry for an improved method of preparing an ion exchange resin catalyst that provides an even distribution of a promoter throughout an ion exchange resin catalyst bed in a rapid manner and without a separate mixing vessel or the addition of gases as described in the prior art.